Whistling air vents

mhjaq8603 · January 25

I have a one pipe steam system. I was having a huge problem with multiple vents hissing and spitting wet steam. I eventually changed out the main vents (2 Hoffman 75s) I have changed out all the air vents on every radiator (Hoffman bullet style 40s). I flushed the boiler because it had dirty water and now it’s all clean. I checked and made sure the pitch was right on all the radiators which stopped some water hammer. I still have 2-3 radiators that whistle when the system heats up. How can I stop this?

bburd · January 25

Possibly the boiler pressure is too high. This can be caused by adjustment of the pressuretrol, or the pigtail that connects the pressuretrol to the boiler may be clogged and not reading the pressure correctly.

Most steam heating systems should run at less than 2 psig; if you have a "vapor" system it may need to run at just a few ounces of pressure using a more sensitive control called a vaporstat.

We can best advise you if you show a photo of your pressuretrol, both from the outside and with the cover removed. Also photos showing the boiler and the piping above it from several angles; step back so we can see from floor to ceiling.

mhjaq8603 · January 25

mhjaq8603 · January 25

mhjaq8603 · January 25

mhjaq8603 · January 25

Captain Who · January 25

Looks like pressuretrol is set as low as it will go. To verify that it is functioning you really need to get a 0-3 or 0-5psi gauge to go on that tree. It ought to be the way the boilers come. I'm assuming you have made sure the pigtail is clear. The 0-30 has to remain there (actually see if you can relocate it though or change that tee to a cross) due to the code requiring a pressure gauge that can go twice as high as the pressure relief valve requirement of 15 psi. They usually clog and are non-functional. Mine is right on the boiler where it easily clogs. I cleared it once and then stopped bothering.

Captain Who · January 25

What is the boiler model and size? You can check the installation manual to see where they advise the height of the close nipple on the Hoffman Loop be. Make sure yours is not too high. If your floor and the boiler are both level it is a matter of measuring from the floor to the top of the close nipple and also measuring from the floor to the NWL normal waterline mark that they usually have on the boiler.

dabrakeman · January 25

Water is very dirty. Did you ever reflush that out, add fresh water, run a few cycles and then skim?

Has the hissing just been bad since the colder weather here in MI or was it persistent even in milder weather?

mhjaq8603 · January 25

The water is crystal clear now, I did a lot of work to get it that way. I literally just took of the pigtail and it was absolutely clogged. I cleaned it out and am now testing. So far seems a lot better. Can you guys suggest a better pressure gage or gauges? I had a little whistle from one radiator vent but it’s significantly better! I have never observed that pressure gage to actually work.

mhjaq8603 · January 25

Now that the pigtail is clear, upon the first firing of the boiler I’m noticing a little steam coming out of one of the main vents. The pressure gauge is actually working a little too.

Captain Who · January 25

Did it successfully reach a cut-out pressure, ie. did the pressuretrol break, and then properly make the circuit at cut-in, even if you can't tell what the actual pressures are on that 0-30 gauge?

I have one Gorton #1 that is allowing a smidgeon of steam to leak before it successfully completely shuts. I'm going to remove it and soak it in vinegar, maybe in my ultrasonic cleaner.

ethicalpaul · January 25

https://www.amazon.com/dp/B0C624GLKD/

mhjaq8603 · January 25

yes it actually cuts out when it’s supposed to!

mhjaq8603 · January 25

Thanks Paul I ordered that one. Should I put it on a tee with the one I already have?

ethicalpaul · January 25

Apparently you have to keep the 0-30psi one on there, so you could add another tee to have them both on there

Whistling air vents

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